Multiple substrate electrical circuit device

ABSTRACT

In one embodiment of the disclosure, a method includes providing a carrier substrate, forming a first region over an upper surface of the substrate, creating an electrical component using a planar process, embedding the electrical component in the dielectric layer, and removing a substrate portion of the electrical component. The first region includes a dielectric layer and may be made of any material that electrically isolates the electrical component from the carrier substrate. The electrical component may be created using a planar process thereby having an epitaxial surface that is embedded in the dielectric layer.

RELATED APPLICATIONS

This application is a divisional of application Ser. No. 11/845,510filed Aug. 27, 2007, entitled “Multiple Substrated Electrical CircuitDevice,” now U.S. Pat. No. 7,825,005.

TECHNICAL FIELD OF THE DISCLOSURE

This disclosure relates to electrical circuit devices, and moreparticularly, to a multiple substrate electrical circuit device andmethod of manufacturing the same.

OVERVIEW OF THE DISCLOSURE

Monolithic microwave integrated circuit (MMIC) devices are a type ofintegrated circuit (IC) device that process electrical signals atmicrowave frequencies. Monolithic microwave integrated circuit devicesmay process analog as well as digital signals in order to provide a widearray of useful applications, such as cellular communications or othermicrowave communication technologies. Due to performance requirements atthese microwave frequencies, monolithic microwave integrated circuitdevices are typically formed on high performance substrates, such asgallium-arsenide, indium-phosphide, indium-nitride, or other similarsubstrate materials having a relatively low noise floor and high currentdensity.

SUMMARY OF THE DISCLOSURE

In one embodiment of the disclosure, a method includes providing acarrier substrate, forming a first region over an upper surface of thesubstrate, creating an electrical component using a planar process,embedding the electrical component in the dielectric layer, and removinga substrate portion of the electrical component. The first regionincludes a dielectric layer and may be made of any material thatelectrically isolates the electrical component from the carriersubstrate. The electrical component may be created using a planarprocess thereby having an epitaxial surface that is embedded in thedielectric layer.

In another embodiment of the disclosure, a semiconductor device includesa carrier substrate, a dielectric layer, and a planarized electricalcomponent. The dielectric layer is disposed over an upper surface of thecarrier substrate. The electrical component is embedded in thedielectric layer and physically isolated from any substrate.

Some embodiments of the present disclosure may provide numeroustechnical advantages. A technical advantage of one embodiment mayinclude an electrical circuit device that may utilize multiple substratetechnologies. While various substrate materials, such as silicon,germanium, gallium-arsenide, and the like may each exhibit differingcharacteristics, the teachings of the present disclosure may allowcombinations of these various substrate technologies in order to furtherenhance the utility that the electrical circuit may provide.

While specific advantages have been disclosed hereinabove, it will beunderstood that various embodiments may include all, some, or none ofthe disclosed advantages. Additionally, other technical advantages notspecifically cited may become apparent to one of ordinary skill in theart following review of the ensuing drawings and their associateddetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of various embodiments will be apparentfrom the detailed description taken in conjunction with the accompanyingdrawings in which:

FIG. 1 is a side elevation, cross-sectional view of a dielectric layerand conductive layer that are formed over the upper surface of a carriersubstrate according to one embodiment of a multiple substrate electricalcircuit device;

FIG. 2 shows an intermediate structure, separate from the carriersubstrate of FIG. 1, having a number of electrical components that havebeen created using any suitable planar process;

FIG. 3 shows the carrier substrate of FIG. 1 and several electricalcomponents from intermediate structure of FIG. 2 that are attached tothe dielectric layer;

FIG. 4 shows the structure of FIG. 3 in which substrate portions of theelectrical components have been removed;

FIG. 5A shows structure of FIG. 4 in which microstrip lines areinterconnected to several electrical components;

FIG. 5B is an enlarged elevational view of FIG. 5A showing oneelectrical component that is attached to dielectric layer;

FIG. 6A shows the structure of FIG. 5A in which thermal bars areattached to electrical components; and

FIG. 6B is an enlarged elevational view of FIG. 6A showing one thermalbar that is attached to electrical component.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

As mentioned previously, monolithic microwave integrated circuit (MMIC)devices are typically formed of high performance substrates in order toprovide adequate performance at microwave frequencies. Nevertheless,many applications for monolithic microwave integrated circuit devicesmay utilize circuitry where the level of performance provided by thesehigh performance substrates are not necessary. For example, a cellulartelephone circuit having microwave circuitry may also include digitallogic to administer the various features available on the telephone.Thus, it would be beneficial to provide a multiple substrate electricalcircuit that may utilize the high performance substrates in conjunctionwith other cost effective substrates, such as silicon or germanium.

FIGS. 1 through 6 are cross-sectional drawings shown during variousphases of manufacture showing one embodiment of a sequence of actionsthat may be performed to create a multiple substrate electrical circuitdevice 10. A carrier substrate 12 may be provided as illustrated inFIG. 1. Carrier substrate 12 may be any suitable semi-conductormaterial, such as silicon (Si), gallium-arsenide (GaAs), Indium-Nitride(InN), germanium (Ge),silicon-germanium (SiGe) silicon-carbide (SiC), orindium-phosphide (InP). In one embodiment, carrier substrate 12 may beformed into an integrated circuit such that one or more electricalcircuit devices are formed on its upper surface 18.

A dielectric layer 16 and conductive layer 28 may then be formed overthe upper surface 18 of carrier substrate 12. Conductive layer 28 may bedisposed over the upper surface 18 prior to forming dielectric layer 16in order to electrically isolate electrical component 14 from carriersubstrate 12. In one embodiment, conductive layer 28 may be made of anysuitable conductive material, such as metal in order to serve as aground plane to electrically isolate circuitry on carrier substrate 12.In another embodiment, a second dielectric layer may be disposed inbetween the conductive layer 28 and upper surface 18 in order to provideelectrical isolation of the conductive layer 28 from the circuitry onthe upper surface 18.

Dielectric layer 16 may be formed of any suitable material. In oneembodiment, dielectric layer 16 may include a number of layers, eachcomprising a differing material. In another embodiment, dielectric layer16 may include a number of layers such that one or more of the layersincludes various passive electrical components, such as resistors,capacitors, or inductors.

FIG. 2 shows an intermediate structure 42, separate from the carriersubstrate 12 of FIG. 1, having a number of electrical components 14 thathave been created using any suitable planar process. Multiple electricalcomponents 14 are formed on an epitaxial surface 34 in a side-by-sideconfiguration on a substrate portion 36. Electrical components 14 may beany type of component, such as a bipolar transistor, field-effecttransistor (FET), resistor, or capacitor and may be formed through theresult of a planar process. Electrical components 14 may be formed fromany suitable semi-conductor material, such as silicon (Si),gallium-arsenide (GaAs), Indium-Nitride (InN), germanium(Ge),silicon-germanium (SiGe) silicon-carbide (SiC), or indium-phosphide(InP). Interface regions 38 are included to illustrate demarcationregions where individual electrical components 14 may be separated fromone another.

In one embodiment, the material from which the electrical component 14is formed may be independent of the material from which the carriersubstrate 12 is formed. That is, the material of the electricalcomponent 14 may be different from the material of the carrier substrate12. Certain embodiments may provide an advantage in that multiplesemiconductor technologies may be combined into an electrical circuithaving a relatively small size. For example, multiple substrateelectrical circuit device 10 may be a monolithic microwave integratedcircuit (MMIC) in which carrier substrate 12 may be made of silicon forprocessing of digital logic signals and electrical component 14 may bemade of gallium-arsenide for processing of microwave frequency signals.Thus, in this particular example, a high performance gallium-arsenideelectrical component 14 such as a transistor may be used in conjunctionwith a relatively low cost silicon carrier substrate 12 in order tocombine the inherent strengths of both types of substrate materials.

FIG. 3 shows carrier substrate 12 and several electrical components 14from intermediate structure 42 that have been separated from one anotheralong interface regions 38. The epitaxial surface 34 of electricalcomponents 14 may be embedded in dielectric layer 16 such that substrateportion 36 of electrical component 14 faces away from dielectric layer16. Next, substrate portion 36 may be physically isolated from substrateportion 36 by removing substrate portion 36 from electrical component 14as shown in FIG. 4. Substrate portion 36 may be removed from electricalcomponent 14 using any suitable approach. In one embodiment, substrateportion 36 may be removed using known chemical etching techniques.Certain embodiments may provide an advantage in that processing theelectrical component 14 in this manner allows thinning of substrateportion 36 without the need for special handling procedures and allowsfor implementation of heat conducting devices, such as thermal bars (tobe described in detail below).

Electrical components 14 may thus be disposed proximate the carriersubstrate 12 by dielectric layer 16. Dielectric layer 16 may be made ofany material that provides electrical isolation of electrical component14 from carrier substrate 12. In one embodiment, dielectric layer 16 maybe made of a material that does not cause undue mechanical interfacestress between electrical component 14 and carrier substrate 12throughout their anticipated thermal temperature ranges. That is,dielectric layer 16 may have sufficient elasticity to compensate forexpansion or contraction of electrical component 14 or carrier substrate12 due to each of their coefficient of thermal expansion (CTE) factors.

In one embodiment, dielectric layer 16 may be made of liquid crystalpolymer (LCP). Liquid crystal polymer is a material that allows forrelatively fine control over the thickness of the dielectric layer 16and is stable over a wide temperature range. Thus, multiple substrateelectrical circuit device 10 may be configured to have relatively stablephysical operating properties by being formed of liquid crystal polymer.Liquid crystal polymer also has a relatively low dielectric constant.The teachings of the present disclosure recognize that materials inclose proximity to electrical component 14 may exhibit an adverse effectupon performance due to parasitic capacitance. Thus, certain embodimentsutilizing a dielectric layer 16 made of liquid crystal polymer mayalleviate the adverse effect of parasitic capacitance by having arelatively low dielectric constant.

FIG. 5A shows multiple substrate electrical circuit device 10 of FIG. 4in which microstrip lines 22 are interconnected to several electricalcomponents 14. In one embodiment, microstrip lines 22 may be used toprovide electrical interconnection of electrical components 14 to othercomponents. For example, although not shown, microstrip lines 22 may beprovided to interconnect electrical components 14 to circuitry oncarrier substrate 12. In another embodiment, microstrip lines 22 may bean antenna that is configured to radiate electro-magnetic energy. In yetanother embodiment, electrical component 14 may be a diode andmicrostrip line 22 may be an antenna that function together as a radiofrequency (RF) detector. FIG. 5B is an enlarged elevational view showingone electrical component 14 that is attached to dielectric layer 16.

The electrical component 14 may be electrically connected to microstriplines 22 by vias 24. Interconnect pads 26 may be provided withelectrical component 14 to allow attachment of the electrical component14 to vias 24. In one embodiment, a second dielectric layer 20 may beformed proximate the interconnect pads 26 to control stray capacitancebetween the microstrip lines 22 and the electrical component 14.

Thermal bars 30 may be disposed on electrical components 14 as shown inFIG. 6A. An enlarged elevational view showing one thermal bar 30 that isattached to electrical component 14 is shown in FIG. 6B. Thermal bars 30may be disposed on electrical component 14 using any suitable approach.In one embodiment, thermal bar 30 may be grown on electrical component14. Thermal bar 30 may provide for the efficient removal of heat incertain embodiments. The thermal bar 30 may provide improved conductionof heat away from electrical component 14 than otherwise would have beenprovided by substrate portion 36 from which the electrical component 14was formed. The thermal bar 30 may also be operable to hermetically sealelectrical component 14 from the detrimental effects of the ambientenvironment, such as moisture or airborne debris.

Multiple substrate electrical circuit device 10 provides forimplementation of differing substrate technologies on a single carriersubstrate 12. Using these differing substrate technologies, applicationsfor the multiple substrate electrical circuit device 10 may be realizedhaving enhanced performance at a relatively lower cost. Attachment ofelectrical components 14 to carrier substrate 12 prior to removal ofsubstrate portion 36 may also alleviate handling problems inherent inknown semiconductor thinning techniques. Removal of substrate portion 36from the electrical component 14 may also allow implementation ofthermal bars 30 to efficiently dissipate heat. Thus, the describedmultiple substrate electrical circuit device 10 may provide severalperformance advantages at a relatively reduced cost.

Although the present disclosure has been described in severalembodiments, a myriad of changes, variations, alterations,transformations, and modifications may be suggested to one skilled inthe art, and it is intended that the present disclosure encompass suchchanges, variations, alterations, transformations, and modifications asfalling within the spirit and scope of the appended claims.

1. A semiconductor device comprising: a carrier substrate of a firstsemiconductor material having a first upper surface; a dielectric layerhaving a second upper surface that is disposed over the first uppersurface; and an epitaxial surface of a second semiconductor materialembedded in the second upper surface of the dielectric layer andelectrically isolated from the carrier substrate, the epitaxial surfaceof the second semiconductor material having a planarized electricalcomponent formed therein.
 2. The semiconductor device of claim 1,wherein the carrier substrate is an integrated circuit.
 3. Thesemiconductor device of claim 2, wherein the electrical component iselectrically connected to the integrated circuit using a microstripline.
 4. The semiconductor device of claim 1, wherein the dielectriclayer is made of liquid crystal polymer.
 5. The semiconductor device ofclaim 1, further comprising a conductive layer in between the firstupper surface and the dielectric layer.
 6. The semiconductor device ofclaim 1, wherein the electrical component is a type of electrical deviceselected from the group consisting of a field effect transistor, abi-polar transistor, a resistor, and a capacitor.
 7. The semiconductordevice of claim 1, further comprising a thermal bar that is attached tothe electrical component.
 8. The semiconductor device of claim 1,wherein the second semiconductor material is selected from the groupconsisting of silicon (Si), gallium-arsenide (GaAs), Indium-Nitride(InN), germanium (Ge), silicon-carbide (SiC), or indium-phosphide (InP).9. The semiconductor device of claim 1, wherein the first semiconductormaterial is different from the second semiconductor material.